HALT and HASS Testing
HALT (Highly Accelerated Life Testing) testing is designed to improve product design by identifying the weak points in a design thereby focusing improvements on only the areas that need them.
HALT testing is designed to fail test samples through aggressive test conditions and profiles. Post test failure analysis is utilized to identify the failure location and failure mode and provide information to improve the product’s design or manufacturing techniques. A few iterations of HALT testing can vastly increase a products durability by identifying areas that need improvement.
HASS (Highly Accelerated Stress Screening) testing is designed to only fail production units that have incipient flaws that would cause “infant mortality” failures in the field. The production units are tested using combined environments, at lower levels and/or durations compared to those used for HALT testing. These tests can be done on a lot sampling basis or for the entire production run.
To accomplish the HALT HASS testing, the chamber contains an electric heat source, pneumatic vibration system and an external liquid nitrogen cooling source:
- Thermal Range: -100°C to +200°C
- Range of Change: Up to 60°C/minute (Unit Under Test (UUT) dependent)
- Vibration: 100 Grms (max. unloaded table @ 25°C)
- Vibration Table: 48" x 48"
Thermal Subsystems
Heating is accomplished by the use of resistive wire heater coils controlled by solid-state relays through the HanseView™ Control System.
Electrical current passing between phases of the supply voltage source, using the heater coil as the path, causes the coil to heat due to the resistance of the coil.
The heated air is transferred by ventilation fans to the UUT through the air plenum. The heated air is recirculated within the chamber to allow greater control of the temperature levels.
Cooling is provided by an external liquid nitrogen source and a control and distribution system. A liquid nitrogen (LN2) coupling to a proportional valve is provided. The proportional valve is controlled by the HanseView Control System. The valve allows LN2 to reach a spray bar equipped with fog nozzles to disburse the LN2 in a gaseous state (GN2) into the air plenum for distribution by the ventilation fans.
The system is configured with three “T” type thermocouples. One of these is connected to a Watlow® Series 97 HI/LO Limit Control and the other two are used by the HanseView Control System to monitor air and product temperature.
Vibration Subsystem
The vibration subsystem utilizes filtered compressed air which is regulated by the HanseView Control System distributed to the table-mounted vibrator assemblies.
The vibration table allows for six degrees of freedom. The system may be used in a manual mode or may be programmed through the HanseView Control System.
The patented vibration table consists of a non-solid aluminum structure design which has 3/8-16 stainless steel inserts located on the UUT side for fixture mounting.
Patented vibrators are held in place by bolts which mount to stainless steel inserts and use shims to help prevent thermal transfer from the table to the vibrator housing. Each vibrator is equipped with a separate manual air valve.
The cell pattern of the table provides for distribution of the shock wave generated by the vibrators and the resulting reflections in a random pattern to all areas of the table. The table is designed to be as rigid as possible and has a high resonant frequency. This design provides for 90% of vibration energy in 5-4000 Hz range for maximum low energy in low frequency range.
Hanseview Control System
Unit Under Test temperature, air temperature, and vibration are controlled by the HanseView/Vibration Research software. This system is a PC-based, Microsoft Windows 95, 98, NT 4.0, 2000, Xp or VISTA operating at 350 MHz or faster.
The programs are written to provide a graphical user interface (GUI) for the control of the chamber. A keyboard is provided to allow data entry and normal system operation.
It should be noted that on demand, the HanseView Control System saves temperature and vibration set points, air and product temperatures, and product vibration level to the PC’s hard drive for the generation of graphs and reports.
DTB engineers can work with you to develop customized test HALT HASS conditions and testing profiles to challenge your product for all modes of failure. Our facilities can handle large items for this type of testing.
Examples of HALT HASS testing conducted at DTB include electrical components, plumbing fixtures, diesel engines and aircraft arresting gear.